The present invention relates generally to a valve unit, and in particular, a valve unit disposed in an ink supply channel for use in connecting an ink-jet recording head and an ink tank, and which is capable of generating a negative pressure.
Conventional ink-jet printers generally include a carriage which is loaded with an ink-jet recording head and an ink cartridge for supplying ink. With the carriage in place, the carriage reciprocately moves along a recording paper and discharges ink drops onto recording paper according to printing data. The recording head discharges the ink drops from nozzle holes by generating a pressure within a pressure generating chamber. The pressure generating chamber communicates with a common ink chamber and the nozzle holes of the recording head.
With such a recording head, since the nozzle hole is normally positioned lower than the ink liquid level in the ink cartridge, the head pressure acts on the nozzle hole and causes the ink to leak out of the nozzle hole. In order to solve this problem, a porous material is usually placed in the ink cartridge, so that the capillary force from the porous material keeps the ink pressure in the ink cartridge slightly lower than the pressure in the recording head.
When the quantity of the ink absorbed into the porous material decreases as ink use increases the capillary force of the porous material delays the supply of ink into the recording head. As a result, the ink in the carriage is not completely used. Another problem associated with the ink carriage is the large size of the ink cartridge required to house the large volume of the porous material.
Generally an ink cartridge is constructed such that a wall having an opening is provided in the lower portion of an ink tank thus dividing the lower portion thereof into an ink reservoir and a cavity. A check valve is installed in the opening of the wall, such that when ink pressure in the recording head is lowered the valve opens, discharges the ink from the reservoir into the cavity and supplies the ink to the recording head.
Accordingly, it is desirable to provide an ink cartridge for an ink-jet recording head, which overcomes the inadequacies of the prior art.